423
CHAPTER ELEVEN
Nervous System II
lumbar region of the back into the pelvic cavity, giving rise
to a number of motor and sensory F
bers associated with the
lower abdominal wall, external genitalia, buttocks, thighs,
legs, and feet. The major branches of these plexuses include
the following
(f g. 11.34)
:
1. The
obturator nerves
supply the adductor muscles of the
thighs.
2. The
femoral nerves
divide into many branches,
supplying motor impulses to muscles of the anterior
thighs and receiving sensory impulses from the skin of
the thighs and legs.
3. The
sciatic nerves
are the largest and longest nerves in
the body. They pass downward into the buttocks and
descend into the thighs, where they divide into
tibial
and
common F
bular nerves.
The many branches of these
nerves supply muscles and skin in the thighs, legs, and
feet.
Superior
gluteal n.
Inferior
gluteal n.
Sacral
plexus
Sciatic n.
Common
Fbular
(peroneal) n.
Saphenous n.
±emoral n.
Obturator n.
Tibial n.
Pudendal n.
Posterior
cutaneous n.
(b)
(c)
(a)
Lateral
femoral
cutaneous n.
±emoral n.
Obturator n.
Superior
gluteal n.
Pudendal n.
Inferior
gluteal n.
Common
fibular
(peroneal) n.
Tibial n.
Sciatic n.
L1
L2
L3
L4
L5
S1
S2
S3
S4
S5
Ventral
rami
Posterior
divisions
Anterior
divisions
FIGURE 11.34
Nerves of the lumbosacral plexus. (
a
) Close up. (
b
)Anterior view. (
c
) Posterior view.
Other nerves associated with the lumbosacral plexus that
innervate various skeletal muscles include the following:
1. The
pudendal nerve
supplies the muscles of the perineum.
2. The
inferior
and
superior gluteal nerves
supply the
gluteal muscles and the tensor fasciae latae muscle.
The ventral branches of the thoracic spinal nerves do not
enter a plexus. Instead, they travel into spaces between the
ribs and become
intercostal
(in
ter-kos
tal)
nerves.
These
nerves supply motor impulses to the intercostal muscles and
the upper abdominal wall muscles. They also receive sensory
impulses from the skin of the thorax and abdomen. Clinical
Application 11.7 discusses injuries to the spinal nerves.
PRACTICE
38
How are spinal nerves grouped?
39
Describe how a spinal nerve emerges from the spinal cord.
40
Name and locate the major nerve plexuses.
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